# Door Frame Material Calculator

> Work out the jamb and head cutting lengths for door frames, the total timber length, and how many stock lengths to buy when the cuts are nested.

Category: Construction · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/door-frame-material-calculator

A door frame or lining is two jambs and a head. Enter the opening size and your stock length; the calculator lists the cuts and packs them into as few stock lengths as it can.

Also called: Door lining calculator, Door jamb calculator.

## Inputs
- Opening width between jambs (unit mm; default 900)
- Opening height (unit mm; default 2100)
- Head housing into each jamb (unit mm; default 32)
- Extra length per jamb (unit mm; default 50)
- Number of frames (default 3)
- Stock length (unit mm; default 5400)
- Waste allowance on length (unit %; default 10)

## Results
- Stock lengths to buy
- Jamb cut length
- Head cut length
- Net length
- Length with waste allowance

## Formula

```
Jamb = H + allowance;  Head = W + 2 × housing;  Net = Frames × (2 × Jamb + Head);  Stock lengths by first-fit decreasing nesting of all cuts
```

Where:
- W, H: opening width and height
- housing: head extension into each jamb

## Worked example
1. Jamb = 2,100 + 50 = 2,150 mm; head = 900 + 2 × 32 = 964 mm.
2. Net = 3 × (2 × 2,150 + 964) = 15,792 mm.
3. Each 5.4 m length takes two jambs and a head (5,264 mm), so 3 lengths.

**Result:** Three 900 × 2,100 mm frames need 3 stock lengths of 5.4 m, about 15.8 m of timber.

## What the result means

Buy the stock-length count; the waste-allowance length is a check for when you buy by the metre. Add a spare length if the timber quality is variable.

## Assumptions and limits
- Saw kerf is ignored.
- Each frame is two jambs and one head of the same section.
- Stops, architraves and thresholds are not included.

## Questions

### Why is the head longer than the opening?

When the head is housed into or runs over the jambs, each end gains the housing depth.

### Why not just divide total length by the stock length?

Cuts cannot be joined, so off-cuts shorter than the next piece are wasted. Nesting the actual cuts gives the true count.

## Related calculators
- [Window Frame Length Calculator](https://calculators.geekmidst.com/calculators/window-frame-length-calculator)
- [Wall Stud Quantity Calculator](https://calculators.geekmidst.com/calculators/wall-stud-quantity-calculator)
- [Material Waste Rate Calculator](https://calculators.geekmidst.com/calculators/material-waste-rate-calculator)

_Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/door-frame-material-calculator